Composite dielectric material doped with rare earth metal oxide and manufacturing method thereof

ABSTRACT

A composite dielectric material doped with rare earth metal oxide and a manufacturing method thereof are provided. The composite dielectric material is doped with nano-crystalline rare metal oxide which is embedded in silicon dioxide glass matrix, and the composite dielectric material of the nano-crystalline rare metal oxide and the silicon dioxide glass matrix is synthesized by the manufacturing method using sol-gel route. The dielectric value of the glass composite dielectric material is greater than that of pure rare metal oxide or that of silicon dioxide. In presence of magnetic field, the dielectric value of the composite dielectric material is substantially enhanced compared with that of the composite dielectric material at zero field.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/075,162, filed on Mar. 29, 2011, the disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a composite dielectric material and amanufacturing method thereof, and more particularly to a compositedielectric material doped with nanoparticles of rare earth metal oxideembedded in silicon dioxide showing colossal dielectric response andmagnetodielectric effect and a manufacturing method thereof.

BACKGROUND OF THE INVENTION

Silicon (Si) element is a type of semiconductor material commonly usedin electronic industries, and can be used as a substrate of asemiconductor wafer which thus can be deposited with various conductivematerial and dielectric material by semiconductor processes, whereinvarious deposited layers thereon are then patterned by suitablephotomask exposure and development processes, so as to constructmulti-layer patterned integrated circuit (IC) structures. After formingthe IC structures, the semiconductor wafer can be cut into a pluralityof chips for being used as active control elements of various electronicproducts.

For a dielectric layer of the semiconductor wafer, the most commondielectric material is silicon dioxide (silica, SiO₂), silicon nitride(Si₃N₄), silicon oxynitride (SiON) and etc. However, with the line-widthminiaturization of IC processes (such as 0.13 μm processes), adielectric layer of SiO₂ with too smaller thickness will cause thephenomenon of electronic breakdown accompanied with very large staticleakage power due to direct tunneling, wherein the direct tunnelingleakage current seriously affects the power consumption of circuitelements which thus lose normal operation functions thereof (such as amemory storage function). Thus, when the thickness of a SiO₂ dielectriclayer of a gate is designed to be smaller than 10 nm, the manufactureruses high-k material to replace traditional SiO₂ material for solvingthe serious phenomenon of direct tunneling leakage current. Under thesame thickness of SiO₂, the high-k material can substantially provide agreater physical thickness to solving the technical problem of directtunneling leakage current.

The common high-k material comprises Al₂O₃, HfO₂, ZrO₂, TiO₂, La₂O₃,Pr₂O₃ or mixture thereof. The foregoing high-k material can be appliedto gate dielectric layers in ICs. For example, the gate dielectriclayers are important structural layers of metal oxide semiconductorfield effect transistors (MOSFETs). Under the same thickness of SiO₂,the quantum tunneling can be up to 1.5 to 2.5 nm. For increasing thespeed of circuit elements and lowering the threshold voltage thereof,the thickness of the gate dielectric layers need to be continuouslylowered. If the gate dielectric layers are thinner, the desire of thegate dielectric layers is stricter, i.e. it needs to use the foregoinghigh-k material to provide a lower leakage current or higher breakdownfield.

Generally, the foregoing dielectric material or high-k material isprocessed by heating silicon substrate, chemical vapor deposition (CVD)or DC magnetron sputtering system to obtain an oxide layer of SiO₂ or ahigh-k coating. However, syntheses and crystallo-chemistries of theforegoing perovskite type compounds are too complicated, while thestability of pure phase thereof, the precise control of composite andoxygen stoichiometry are also very difficult. Therefore, it needs to useamorphous high-k oxide candidates with superior phase stability fordesigning and assembling multifunctional devices that operate at highertemperatures. In addition, the superior electronic performance of Si inparticular the Si surface that is realized with an SiO₂ overlayer, theSi—SiO₂ interface, has not been achieved with any othersemiconductor-dielectric combination to this day. SiO₂ effected aseemingly magical improvement in the electrical characteristics of theSi surface compatible with planarization technology. Future CMOSgenerations may be enhanced by nanocrystalline high-k dielectrics, andadded functionality and flexibility may be achieved throughoxide/silicon/oxide heterostructures for quantum-effect devices.

Recently, there has been a trend of development of magnetic nanoparticlein nonmagnetic dielectric matrix to tailor desired magnetic, dielectric,and other properties depending on the concentration of the magneticions. However, these types of perovskites possess compositionalvariations, structural inhomogeneities, or phase heterogeneities inphysical scale from micron or submicron range to the atomic level. Thissuggests that the high-k value and MD behavior of aforementioned complexsystem is not a fundamental property but is rather an artifactassociated with mesoscopic heterogeneities of the system. Therefore,searching for alternative materials containing single-valent ions withphase stability would be highly desirable.

As a result, it is necessary to provide a semiconductor wafer havingdielectric layers showing colossal magnetodielectric effect and amanufacturing method thereof to solve the problems existing in theconventional technologies, as described above.

It is found by the present invention that magnetic rare earth oxides(RE₂O₃, RE means lanthanoids, i.e. a series of 10 elements from La to Luin the periodic table) can be embedded into SiO₂ glass matrix to formcomposite of super-paramagnetic nanoparticles showing colossalmagnetodielectric (MD) effect, wherein the colossal MD behavior in thisglassy system is related to the magnetic spin and the dipole couplingthrough the lattice, so as to be able to develop magnetoresistancechange effects associated with nanoparticles size and concentration.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide a compositedielectric material doped with nanoparticles of rare earth metal oxideembedded in silicon dioxide showing colossal dielectric response andmagnetodielectric effect and a manufacturing method thereof, whereinnanoparticles of rare earth oxides (RE₂O₃, RE means lanthanoids, i.e. aseries of 10 elements from La to Lu in the periodic table) can beembedded into SiO₂ glass matrix by using sol-gel route, so as to form aglass composite system used as composite dielectric material which isalso applied to a dielectric layer of a semiconductor wafer. Thecomposite dielectric material can show colossal dielectric response andmagnetodielectric effect under an externally applied magnetic field, sothat it can increase the dielectric coefficient of the dielectric layerof the semiconductor wafer and lower the leakage current and powerconsumption thereof. As a result, it is advantageous to develop amultifunctional integrated circuit which can normally operate at roomtemperature or higher temperature.

To achieve the above object, the present invention provides a compositedielectric material doped with nanoparticles of rare earth metal oxideembedded in silicon dioxide showing colossal dielectric response andmagnetodielectric effect, which comprises a matrix and a plurality ofnanoparticles, wherein the matrix comprises silicon dioxide (SiO₂), thenanoparticles comprise at least one type of rare earth metal oxide, andthe particle diameter of the nanoparticles is ranged from 2 nm to 10 nm.

In one embodiment of the present invention, the rare earth metal oxideis selected from erbium oxide (Er₂O₃), europium oxide (Eu₂O₃) or themixture thereof.

In one embodiment of the present invention, the composite dielectricmaterial is applied to a dielectric layer of a semiconductor wafer,wherein the wafer has a surface and the dielectric layer is formed onthe surface of the wafer, the dielectric layer comprises a glasscomposite of the rare earth metal oxide and silicon dioxide of thenanoparticles in the composite dielectric material.

In one embodiment of the present invention, the surface of the wafer hasat least two electrode layers, and the dielectric layer is disposedbetween the electrode layers.

In one embodiment of the present invention, the surface of the wafer hasa plurality of electronic elements which pass through the dielectriclayer to be electrically connected the at least two electrode layerswith each other.

In one embodiment of the present invention, the nanoparticles are aglass composite of the rare earth metal oxide and silicon dioxidedifferent from the silicon dioxide of the matrix.

On the other hand, the present invention provides a manufacturing methodof composite dielectric material doped with nanoparticles of rare earthmetal oxide embedded in silicon dioxide showing colossal dielectricresponse and magnetodielectric effect, which comprises steps of: mixingtetraethylorthosilicate (TEOS) and at least one type of rare earth metalchloride into a silica gel; and processing the silica gel by calcinationto reach a predetermined calcination temperature ranged from 700° C. to1200° C., so that the silica gel is converted into nanoparticles of aglass composite of rare earth metal oxide and silicon dioxide to thusform a composite dielectric material having the rare earth metal oxide,wherein the particle diameter of the nanoparticles is ranged from 2 nmto 10 nm.

In one embodiment of the present invention, the rare earth metal isselected from erbium (Er), europium (Eu) or the mixture thereof.

In one embodiment of the present invention, the composite dielectricmaterial is applied to a surface of a semiconductor wafer to form adielectric layer, and the dielectric layer comprises the glass compositeof the rare earth metal oxide and the silicon dioxide of the compositedielectric material.

In one embodiment of the present invention, the concentration of therare earth metal chloride doped in the TEOS is ranged from 0.1 mole % to1.0 mol %, such as 0.5 mol %.

In one embodiment of the present invention, the concentration of thenanoparticles of the rare earth metal oxide doped in the silicon dioxideis ranged from 0.1 mole % to 1.0 mol %, such as 0.5 mol %.

In one embodiment of the present invention, before processing the silicagel by calcination, keeping stationary to dry the silica gel of the TEOSand the rare earth metal chloride.

In one embodiment of the present invention, when processing the silicagel by calcination, the silica gel of the TEOS and the rare earth metalchloride is processed by multi-step calcinations to form the compositedielectric material doped with the nanoparticles of the rare earth metaloxide embedded in the silicon dioxide.

In one embodiment of the present invention, after forming the compositedielectric material, further comprising: mixing the glass composite ofthe rare earth metal oxide and the silicon dioxide with TEOS in anothersol-gel process to obtain a mixture solution; applying the mixturesolution onto a surface of a semiconductor wafer by spin coating to forma silica gel layer; and processing the silica gel layer by calcination,so as to form a dielectric layer having the glass composite of the rareearth metal oxide and the silicon dioxide and a silica matrix, whereinthe silicon dioxide of the silica matrix is different from the silicondioxide of the nanoparticles of the glass composite.

DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a TEM microscopic image of an Er05-8 sample according to apreferred embodiment of the present invention, wherein an upper rightinset figure is a particle size distribution histogram of the sample;and a lower right inset figure is a HRTEM (high resolution TEM)microscopic image of the sample;

FIG. 1( b) is a selected-area electron-diffraction (SAED) pattern of thesample according to the preferred embodiment of the present invention;

FIG. 1( c) is a curve diagram of XRD patterns of Er05-7, Er05-8 andEr05-12 samples according to the preferred embodiment of the presentinvention;

FIG. 2 is a magnetic hysteresis diagram of the Er05-8 sample recorded atdifferent temperatures according to the preferred embodiment of thepresent invention, wherein an upper left inset figure is an enlargedrelationship diagram of mass-magnetization (σ) vs. magnetic field (H) ina region close to the coercive field value, and a lower right insetfigure is a relationship diagram of mass-magnetization (σ) vs. magneticfield/temperature (H/T) at different temperatures;

FIG. 3( a) is a relationship diagram of the dielectric value (ε′) andthe absolute temperature (T) of the Er05-8 sample at differentfrequencies according to a preferred embodiment of the presentinvention;

FIG. 3( b) is a relationship diagram of ln(e′⁻¹−ε′_(m) ⁻¹) vsln(T−T_(m)) at temperatures higher than the absolute temperature (T_(m))for the Er05-8 sample at different frequency values according to thepreferred embodiment of the present invention;

FIG. 3( c) is a curve diagram of a dielectric hysteresis loop showingFEL behavior according to the preferred embodiment of the presentinvention;

FIG. 3( d) is a relationship diagram of the dielectric value (ε′) andthe absolute temperature (T) of the Er05-12 sample and pure bulk Er₂O₃material according to the preferred embodiment of the present invention,indicating similar non-FEL feature;

FIG. 3( e) is a relationship diagram of the dielectric value (ε′) andthe absolute temperature (T) of the Eu05-8 sample at differentfrequencies according to the preferred embodiment of the presentinvention;

FIG. 4( a) is a curve diagram of the dielectric loss tangent tan δ ofthe Er05-8 sample at different frequencies according to the preferredembodiment of the present invention;

FIG. 4( b) is a curve diagram of the representative Arrhenius plot ofthe relaxation time of the Er05-8 sample according to the preferredembodiment of the present invention, wherein activation energy values(eV) in each peak values are illustrated;

FIG. 5 is a curve diagram of temperature dependence of ac conductivity(σ_(ac)) of the Er05-8 sample at various frequencies according to thepreferred embodiment of the present invention, wherein a lower rightInset figure is an optical absorption spectra of the Er05-8 sample atroom temperature;

FIG. 6 is a curve diagram of temperature dependence of grain resistance(R_(g)) of erbium oxide calculated from an impedance complex plane plotsaccording to the preferred embodiment of the present invention, whereinan upper right inset shows a schematic model of equivalent electricalcircuits;

FIG. 7( a) is a curve diagram of dielectric value (ε′) and the absolutetemperature (T) of the Er05-8 sample measured under different appliedmagnetic fields at a fixed frequency (2.5 kHz) according to thepreferred embodiment of the present invention, wherein an upper leftinset figure is the variation of the inverse of dielectric value (ε′)with temperature, exhibiting the Curie-Weiss behavior; and a lower leftinset figure is the dielectric strength (Δε′/ε′) of the Er05-8 sample,showing linear variation with the square of magnetization (M²), measuredin the vicinity of T_(m)(˜275 K);

FIG. 7( b) is a curve diagram of dielectric value (ε′) and the absolutetemperature (T) of the Er05-7 sample measured under a 9 T appliedmagnetic fields at various frequency (kHz) according to the preferredembodiment of the present invention;

FIG. 7( c) is a curve diagram of dielectric value (ε′) and the absolutetemperature (T) of the Er05-8 sample measured under a 9 T appliedmagnetic fields at various frequency (kHz) according to the preferredembodiment of the present invention;

FIG. 8 is a curve diagram of temperature dependence of grain resistance(R_(g)) of erbium oxide calculated from an impedance complex plane plotswith external magnetic field according to the preferred embodiment ofthe present invention, wherein an upper right inset figure is thetemperature dependence of ac conductivity (σac) at a fixed frequency(2.5 kHz) with various externally applied magnetic fields; and

FIG. 9 is a schematic view of a glass composite system of erbium oxideand silicon dioxide nanoparticles applied to a dielectric layer of asemiconductor wafer according to the preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The structure and the technical means adopted by the present inventionto achieve the above and other objects can be best understood byreferring to the following detailed description of the preferredembodiments and the accompanying drawings.

In the present invention, super-paramagnetic nanoparticles of rare earthmetal oxides (such as erbium oxide Er₂O₃ or europium oxide Eu₂O₃) areevenly embedded into a silica (SiO₂) glass matrix to form a compositedielectric material showing colossal magnetodielectric (MD) effect,wherein the composite dielectric material can be applied to a dielectriclayer of a semiconductor wafer. This colossal MD behavior in this glassysystem is related to the magnetic spin and the dipole coupling throughthe lattice, so as to be able to develop magnetoresistance changeeffects associated with nanoparticles size and concentration. Forexample, a sol-gel technique can be used to cause the growth of Er₂O₃magnetic oxides in inorganic silica matrix. Among various rare earthoxides, Er₂O₃ has the highest MD effect, the highest resistivity(10¹²-10¹⁵ cm⁻³), a larger band gap (E_(g)=5-7 eV), a static dielectricconstant value (k) about 14, good thermodynamic stability with siliconand etc. The sol-gel process can provide a convenient way for designingrare earth metal oxide nanoparticles with nearly uniform sizes andhomogeneous dispersion in the silica matrix. Thus, the present inventionwill describe the sol-gel process used for the preparation of rare earthmetal oxide nanoparticles in SiO₂ matrix more detailed hereinafter.

The present invention will provide a preferred embodiment hereinafter,wherein the erbium oxide Er₂O₃ is exemplified to explain the technicalconcept of the present invention. In the preferred embodiment of thepresent invention, a composite system of erbium oxide and silica glassshowing colossal magnetodielectric behavior can be synthesized at roomtemperature under atmospheric condition by a simple and economicsingle-step process. Firstly, a silica gel doped with erbium oxide isprepared by tetraethylorthosilicate (TEOS, i.e. Si(OC₂H₅)₄) and thedopant of erbium chloride (ErCl₃), wherein the dopant concentration oferbium chloride is preferably ranged from 0.5 mol %, and the remainingis 99.5 mol % silica (SiO₂); and wherein erbium chloride will beconverted into erbium oxide after being treated at high temperature bythe following calcination. The manufacturing method of the presentinvention is based on a hydrolysis of precursors (TEOS), a watercondensation of hydrolyzed TEOS and an alcoholic condensation thereof,wherein the foregoing reactions are carried out in a medium containing ahydro-alcoholic solution of erbium salt and are listed, as follows:

Hydrolysis of TEOS:

Si(OC₂H₅)₄+4nH₂O→nSi(OH)₄+4nC₂H₅OH

Water condensation:

nSi(OH)₄→nSiO₂+2nH₂O

Alcoholic condensation:

nSi(OC₂H₅)₄+2H₂O→nSiO₂+4nC₂H₅OH

After finishing the sol-gel step, the composite of erbium oxide andsilica glass of the present invention is dried at room temperature about3 to 6 weeks, so as to obtain a monolithic transparent gel sample. Then,the room temperature is gradually raised to a high temperature toprocess the composite of erbium oxide and silica glass is calcined (i.e.annealed) by multi-step calcinations, to reach different predeterminedmaximum calcination temperatures (700° C., 800° C., 900° C. and 1200°C.), as shown in the following temperature raising flowchart, whereintemperature raising speed (° C./min) and duration (hours) of each oftemperature raising steps is different from each other, but thedifference value is not limited thereto. The silica gels doped witherbium calcined by the three different maximum calcination temperaturesare also called Er05-7, Er05-8 and Er05-12 in turn hereinafter, whereinthe Er05-7, Er05-8, Er05-9 and Er05-12 represent that three embodimentsof composite samples of erbium oxide and silica glass having 0.5 mol %Er₂O₃ are prepared under different predetermined maximum calcinationtemperatures (700° C., 800° C., 900° C. and 1200° C.) in turn.

When the silica gels doped with erbium and prepared by the sol-gel routeare calcined at about 400° C., the silica gels doped with erbium willbecome porous, and the pores thereof start to collapse at about 700° C.With raising the temperature, the functional group “≡Si—OH” will becondensed into “≡Si—O—Si≡”, so as to enhance the collapse of the pores,wherein ions of the rare earth metal oxide are only loosely attached tothe vicinity of the pores. The nano-scale dimensions of the clustersreside of the rare earth metal oxide depend upon the annealingtemperature thereof. For example, at a higher temperature (such as 800°C.), collapse of larger pores will take place, while more Er-ions areagglomerated to form nanoparticles with greater size. Thus, at a furtherhigher temperature (such as 1200° C.), Er₂O₃ nanoparticles in the silicamatrix will grow into a further greater size. After finishing themulti-step calcination, irregular mass of composite of erbium oxide andsilica glass can be obtained.

To understand properties of the silica gel samples doped with erbium,powder XRD of the samples is performed by using CuK_(α) radiation. Anultra high resolution TEM (HRTEM, Model: JEM-3010, JEOL) is used toanalyze the detailed structure of the Er05-7 and Er05-8 samples. Opticalabsorption spectra were carried out by using a UV-visible spectrometer(Model: 2101 PC, Shimadzu) within the 200-900 nm region. The magnetichysteresis measurements were performed in a SQUID magnetometer (Model:MPMS-XL, Quantum Design) with temperatures varying from 2 to 300 K,equipped with a superconducting magnet producing fields up to ±6 T. TheMD measurements were carried out with a LCR meter (Model No. E4980A,Agilant) in conjunction with a cryostatic arrangement integrated to thephysical properties measurement system (PPMS) (Model: 6000, QuantumDesign) configured up to 9 tesla (T) magnetic field. Ferroelectric loopmeasurement was carried out by using a Precision LC meter (Model:609E-6, Radiant Technologies). The present invention concentrates thevariations in temperature and frequency dependent MD properties mainlyon the Er05-8 sample for clarity and compare the analysis with Er05-7,Er05-9, and Er05-12 hereinafter.

Firstly, properties of the erbium-doped silica gel sample measured byTEM, XRD and SQUID are described, as follows: Referring now to FIG. 1(a), the TEM image of the powder specimen of the Er05-8 sample showsnearly spherical nanoparticles of Er₂O₃ in the particle size range ofabout 3-6 nm present in the glass matrix. As shown in the upper rightinset figure of FIG. 1( a), the particle size distributions histogram ofthe sample is illustrated. As shown in the lower right inset figure ofFIG. 1( a), a HRTEM (high resolution TEM) microscopic image of thesample (Er₂O₃ nanoparticles) is illustrated, and shows clear latticefringes with interplanar spacing (3.05 Å) which agrees with the dspacing confirming the presence of nanocrystalline phase. Referring nowto FIG. 1( b), the selected-area electron-diffraction (SAED) pattern ofthe sample shows spotted ring patterns suggesting the development ofregions of localized crystallinity.

Referring now to FIG. 1( c), the curve diagram of XRD patterns of thehigh temperature annealed system Er05-12 sample (3) is illustrated,wherein the XRD patterns of the Er05-12 sample is crystalline with quitelarge Er₂O₃ nanoparticles (>40 nm) which thus clearly exhibits the mostintense characteristic line corresponding to the single phase Er₂O₃ at2θ about 29.30° (peak value: 222). Applying the well-known Scherrer'sequation, sizes of Er-oxide nanoparticles (Er05-12) are also estimatedfrom the integral breadths of the lines as shown in Table 1. The XRDpatterns of Er05-7 and Er05-8 samples cannot be well resolved due totheir amorphous like character. Only a very feeble broad peak can betraced with great difficulty in the XRD domain, 2θ=10°-65°. It isconfirmed that the sizes of Er₂O₃ nanoparticles embedded in the silicaglass matrix grow larger for samples calcined at higher temperatures.

TABLE 1 Powder XRD and TEM structural data, dielectric coefficient (k),phase transition temperature, and other parameters of themagnetodielectric glass composite system of Er₂O₃:SiO₂: Curie-Weissfitting Particle Particle Temp of parameters size size Magnetic Max MaxCurie-Weiss Curie- Interplanar [nm] [nm] field dielectric dielectricTemp Weiss intercept (from (from Intensity H value value T_(o) ConstantC Sample (h k l) XRD) TEM) (Tesla) ε_(max) T_(max) (K) (K) (K) Er05-7 —Predominantly ≈2 0 369 255 — — amorphous 5 571 255 9 763 260 Er05-8 —)Predominantly ≈5 0 284 270 260.06 3968.82 amorphous 5 570 280 270.126211.29 9 724 280 271.64 6918.04 Er05-12 (2 1 1), >40 — 0 — — — — (2 22), (4 0 0), (4 4 0), (6 2 2)

The magnetic-field (H) dependence of the magnetization of the Er05-8sample is carried out in the magnetic field range of ±6 tesla and atdifferent temperatures. Referring now to FIG. 2, the magnetization loop(zero area) obtained up to 5 K displays characteristics ofsuperparamagnetism. Moreover, as shown in the lower right inset figureof FIG. 2, the relationship of mass-magnetization (σ) vs magneticfield/temperature (H/T) at different temperatures is linear andcollapses to a single curve indicating the presence ofsuper-paramagnetic phase of Er₂O₃ nanoparticles (NPs) embedded in SiO₂glass matrix. At the temperature 2 K, hysteretic behaviors are observedand the coercive field is found to have a non-zero value (H_(c)=0.020tesla). It means that the NPs are going to be the magnetically orderedstate at 2 K. As shown in the upper left inset figure of FIG. 2, anenlarged relationship diagram of mass-magnetization (σ) vs. magneticfield (H) in a nearly central region is illustrated, wherein it isevident from the bulging of the hysteresis loop near the central regionand also the magnetic moment/unit mass is enhanced compared to othermeasuring temperature. The hysteresis curves of FIG. 2 do not show anymagnetic saturation in the magnetic field range of ±6 tesla, from whichit is inferred that the Er₂O₃ NPs contained in the samples possess largean isotropic fields.

Then, for dielectric spectroscopy, referring now to FIG. 3( a), thetemperature dependence of the real part of the relative dielectricconstant (c′) of the Er05-8 sample in absence of magnetic field atseveral frequencies (2.5 kHz to 100 kHz), logarithmically separated byone decade, is illustrated, wherein the shape of the curves has a welldefined maximum dielectric value (e′_(m)) at T_(m) about 270° K, and thefrequency dependence indicates the phenomenon of dielectric relaxation.However, a notable broadening around the maximum dielectric value(ε′_(m)) is indicative of a diffuse phase transition (DPT) presence withhigh dielectric constant (ε′), quite different and much higher from purebulk Er₂O₃. From DPT theory, in order to characterize the phasetransition, the empirical expression can be used, as follows:

ε′⁻¹−ε′_(m) ⁻¹ =C _(i)(T−T _(m))^(γ)

wherein γ is the diffuseness exponent indicative of degree of disorder;C_(i) is a temperature independent co-efficient (in general, dependentof frequency); and ε′^(m) is the maximum value of dielectric constant(ε′) at T_(m). For γ=1, there is a normal Curie-Weiss behavior; and forγ=about 2, it implies a typical DPT for the ideal ferroelectric relaxor.

Referring now to FIG. 3( b), a relationship diagram of ln(ε′⁻¹−ε′_(m)⁻¹) vs ln(T−T_(m)) at temperatures higher than the absolute temperature(T_(m)) for the Er05-8 sample at different frequency values, wherein alinear fitting for the Er05-8 sample can obtain that γ=1.84, which isclose to the relaxor value. Any space-charge or interfacial polarizationis not responsible the enhancement of dielectric constant below T_(m).referring now to

FIG. 3( c), it should be noted that the temperature and frequencydependent dielectric constant (ε′) of the corresponding highertemperature calcined Er05-12 sample does not show this DPT behavior, butis similar to pure bulk Er₂O₃ and unlike other two lower calcinedsamples. This indicates that DPT character disappears with growingcrystalline Er₂O₃ clusters (i.e. with increasing calcination temperatureof the prepared sol-gel glass). The critical calcinations temperatureabove which DPT behavior completely diminishes for this typicalconcentration of Er₂O₃ (about 0.5 mol %) is found to be around 1000° C.The DPT behavior is thus confined to the low temperature calcined system(<1000° C., such as between 700° C. and 1000° C.) only where thenanoparticles are in the 2-10 nm range and the system is in thesuper-paramagnetic phase.

Referring now to FIG. 3( d), to check the possible ferroelectriccorrelation, hysteresis loop is also observed, which represents apolarization cycle using higher polarization frequency (2000 Hz) andapplied electric field up to ±2.0 kV/cm, wherein remnant polarizationvalue (Pr) is about 0.032 μC/cm², and coercive field (Ec) is about 0.78kV/cm at 275 K. The relatively narrow polarization electric field (P-E)loop without saturation demonstrates a non-canonical FEL behavior. Thehysteresis loops are very spurious artifact that resemble trueferroelectric, and look very much like those of a lossy dielectric. Inthis nanoparticle-glass composite system (0.5 mol % Er₂O₃:99.5 mol %SiO₂), the concentration of Er₂O₃ nanocrystalline is very small.Moreover, the polarization-electric field characteristics are studiedusing higher polarization frequency (2000 Hz), wherein the maximumfrequency limit is due to the used instrument (Precision LC meter,Radiant Technologies). The high frequency hysteresis loop will be moreclosely related to the intrinsic ferroelectric switching processes thanthe low frequency counterpart, while the results of hysteresis loopindicates that temperature decreasing suggests ferroelectric-likeordering in the Er05-8 sample.

On the other hand, when the rare earth metal oxide-glass sample of thepresent invention is the Eu05-8 sample (i.e. a experimental sample with0.5 mol % Eu₂O₃ prepared at a maximum calcination temperatures 800° C.)for experiments, referring now to FIG. 3( e), the temperature dependenceof the real part of the relative dielectric constant (ε′) of the Eu05-8sample in absence of magnetic field at several frequencies (0.1 kHz to100 kHz), logarithmically separated by one decade, is illustrated,wherein the shape of the curves has a well defined maximum dielectricvalue (ε′_(m)) at Tm about 270 K, and the frequency dependence indicatesthe phenomenon of dielectric relaxation. Similar to Er₂O₃, Eu₂O₃ has adiffuse phase transition (DPT) presence with high dielectric constant(ε′), quite different and much higher from pure bulk Eu₂O₃.

To understand the role of the relaxation dynamics, referring now to FIG.4( a), the temperature dependence of the dielectric loss tangent (tan δ,i.e. leakage constant ratio, the ratio is 1 at room temperature) isshown for various frequencies. The main feature of tan δ is the twomaximum peak values, wherein the peak A is at about 180 K, and the peakB is at about 260 K, wherein the leakage status of the peak B is verysmall) of tan δ which shift to higher temperatures as the frequency isincreased. The peak intensity of the peak A is weaker (about 0.15) thanthat of the other peaks at high temperatures, while high dielectricleakage peak at elevated temperature peak (peak C>320 K) is shifted tolower temperature with increasing frequency. Thus, the loss-peakpositions can be obtained from the frequency and temperature-dependentplot.

Referring now to FIG. 4( b), the resulting temperature dependence (τ) isshown in an Arrhenius representation. Near the DPT temperature (T_(m)),thermally activated behavior with an energy barrier E_(relax) of about1.13 eV can be shown as the following equation: τ=τ_(o)exp(E_(relax)/kT). However, above 300 K, the temperature dependence (τ)becomes reversed with activation energy 1.21 eV. Thus, it shows thatdielectric relaxation process is closely associated with the presence ofthermally activated oxygen vacancies. In the present invention, thedielectric constant relationship of the nanoparticle-glass system isalso studied with different thickness of the samples and with differentelectrode materials, wherein dielectric constant changes are found to bewithin experimental errors indicating intrinsic nature of this system.

Referring now to FIG. 5, the real part of conductivity (σ_(ac)) of thecomplex ac conductivity (σ*) at various frequencies is illustrated. Whenσ_(ac) ∝ε″×f, the temperature dependence of σ¹(T) is identical to thatof the dielectric loss. At higher frequency dependence of conductivity(σ′) can be described by the so-called universal dielectric response(UDR) with the addition of a dc conductivity, σ_(ac)=σ_(dc)+σ_(o) f^(s)(where σdc=dc bulk conductivity; (σo=constant; and s=exponent).Relaxation features seen in ε′(T) should be accompanied by peaks inσac(T) consisting of two temperature regions, shifting with frequency tothe higher temperature.

The Maxwell-Wagnar (MW) effect or the interfacial phenomena model isusually adopted to explain the dielectric relaxation phenomena with highpermittivity. This nano-glass composite system basically comprises amixture of magnetic nanocrystalline Er₂O₃ grain separated by moreinsulating inter-grain (SiO₂ matrix). Such an increase in the dielectricconstant with DPT behavior may be a signature of the effect of internalbarrier layer capacitance (IBLC), which is directly proportional to theratio of the grain size and the grain boundary thickness. Then,referring now to FIG. 6, the impedance data are analyzed using anequivalent circuit consisting of two parallel resistor-capacitor (RC)elements connected in series. One RC element (R_(g) and C_(g))corresponds to the more conductive region (Er₂O₃ nanoparticles) and theother RC element (R_(gb) and C_(gb)) corresponds to the more resistivepart (SiO₂ matrix) of the sample. Each of the RC elements generallygives rise to an arc in the complex impedance Z″-Z′ plane. The impedancespectroscopic data are analyzed with the help of commercial software(Z-VIEW, version 2.9c). According to the popular technique of explainingimpedance spectra in the complex Z″-Z′ plane, the high frequency arc isrelated to the grain (intrinsic effect). At low temperature (T_(m)<270K), almost the entire measured frequency region (20-2×10⁶ Hz) isdominated to have the grain response, governed by the intrinsic effect.

As shown in FIG. 6, it shows that the contribution of grain (Er₂O₃)resistance (R_(g), values obtained from equivalent circuit model) of theEr05-8 sample is used as a function of measuring temperature, whereinR_(g)(T) reveals transition (about 270 K) coinciding with the Tm ofε′(T) as well as σ_(ac). These experimental results imply that thenature of charge carries responsibility for dielectric relaxation peaksand dc conduction belongs to the same category, which indicates that thepolarization relaxation has a close relation with the conductivity ingrain interior, and the polarization process probably depends on theconducting of the charge in the grain interior.

Referring now to FIG. 7( a), about the magnetodielectric (MD) effect,the present invention also shows large increase of dielectric value (ε′)under an externally applied magnetic field for the Er05-8 nanoparticles.A large increase of dielectric value (ε′) (about 2.75 times) under amagnetic field of 9 T observed around the transition temperature region240-280 K at 2.5 kHz. As shown in upper left inset figure of FIG. 7( a),the field dependent inverse of dielectric constant with temperature isalso found to fit the Curie-Weiss law with Curie constant (C) andCurie-Weiss temperature (T₀), as shown in Table 1. It should be notedthat both of the dielectric peak temperatures T_(m) and T₀ shift tohigher temperature regions with increasing magnetic field. Thisindicates that magnetic spins ordering occurs at higher temperatureunder magnetic field, and thus spin-lattice coupling is reduced undermagnetic field.

Referring now to FIGS. 7( b) and 7(c), temperature and frequencydependent dielectric constant is measured at a typical higher magneticfield (about 9 tesla) for two samples. It is observed that thedielectric value (ε′) is larger in the lower temperature annealedsamples (i.e. particle size dependent effect of (ε′)). It is importantto mention that the increase of nanocrystal size by long time annealingthe glass system cause the above mentioned DPT as well as MD effect todecrease and ultimately disappear if the dielectric value (ε′) reducedto that of the pure bulk crystalline Er₂O₃.

As shown in the lower left inset figure of FIGS. 7( a), to furtherclarify the character of the MD effect, the field dependentmagnetodielectric strength can be measured and defined by the followingfunction of the square of the magnetization (M²) near T_(m) (about 275K):

Δε′(H)/ε′(0)=[ε′(H)−ε′ (0)]/ε′(0)

This behavior can also be calculated by the scaling function, asfollows:

$\frac{{\Delta ɛ}^{\prime}}{ɛ^{\prime}} \approx {\alpha \; M^{2}}$

wherein α is about 0.782 and related to the magneto-electric interactionconstant and magneto-striction effect. This measurement suggests thatthe dielectric properties of magnetic nanoparticles are closely relatedto the disposition of the magnetic moments in the sample system. Thus,in the present sample system, the MD effect is related to thesuper-paramagnetism, typical size and concentration of the nanoparticlesof the guest oxide (Er₂O₃) and SiO₂ host glass.

Referring now to FIG. 8, the values for temperature dependentnanocrystalline Er₂O₃ resistance (R_(g)) is obtained from equivalentcircuit element along with ac conductivity in presence of an externallyapplied magnetic field, wherein a huge remarkable magnetic-fieldinfluence feature is shown. A strong positive magnetoelectricinteraction constant is observed, while the observed MD effect is causedessentially through the combination of magnetoresistance andMaxwell-Wagnar (MW) effect. When the nanocrystalline Er₂O₃ resistancedecreases with the increase of externally applied magnetic field (i.e.negative magnetoresistance), the dielectric constant increases with theincrease of the externally applied magnetic field (i.e. positivemagnetodielectric effect). Enhancement of the MD effect through theresistance ratio might imply the possible tunability of the resistive MDeffect. The nanocrystalline Er₂O₃:SiO₂ can be spontaneously(self-organized) formed with almost equal size and separation pitch in anatural way. It is intrinsic to the material, which could be modified bywell-controlled nanoparticle size with separation pitch.

The foregoing observations demonstrate that the coupling betweenmagnetic and dielectric properties of nanoparticles is apparently ageneral feature of the present invention. Moreover, the particle size,separation pitch and concentrations of the Er₂O₃ nanocrystalscontributing to the magnetically and electrically responded permittivityare all easily controllable with annealing temperature and dopingconcentration. Furthermore, the MD effect and super-paramagneticbehavior of the present invention is distinguished from other systemsshowing MD behavior, and can be diminished with growth of nano-clustersize by long time annealing the glass. Besides, the dielectric responseof the Er05-12 sample has no any DPT (along with magnetic field effect),although it is contained Er₂O₃ nano-grain (particle size>40 nm)separated by SiO₂ barrier. As the crystal size increases, the DPTbehavior and the associated MD effect decreases, and ultimatelydielectric constant become equal to be their pure bulk crystallinecounterparts (without silica matrix). However, this finding cannot beclassified by the aforementioned Maxwell-Wagner contribution.

In an alternative possibility, the conduction mechanism is closelyrelated to the oxygen vacancies. Thermally activated reorientation ofdipole moment via the vacancy jumping (i.e. the oxygen ion jumpingthrough the oxygen vacancy) is suggested as the origin of the dielectricrelaxation with activation energy (about 0.7-1.2 eV). In addition, thepossibility of the contact between the electrodes and samplesinfluencing the dielectric properties is excluded by using differentthickness of the samples and with different electrode materials.Furthermore, with increase of cluster size of the glass sample obtainedby higher calcination temperature in atmosphere, the DPT is graduallysuppressed, and eventually disappears in the Er05-12 sample.

Returning to the dielectric relaxation in the Er₂O₃:SiO₂ nano-glasscomposite system, both of the Maxwell-Wagnar mechanism and thereorienting dipole-centre model can be used to explain the main featuresof colossal room-temperature magnetodielectric response. However, thepresent invention also has further studies and experiments withdifferent rare earth metal oxide systems having different concentrationto research the origin and application feasibility of the richdielectric material.

As described above, according to the present invention, it cansynthesize super-paramagnetic nanocrystalline Er₂O₃ particles in silicaglass by a sol-gel method at calcination temperatures between 700° C.and 900° C., such as 700° C., 750° C., 800° C., 850° C. or 900° C., soas to prepare the composite dielectric material, wherein Er₂O₃nano-crystals in larger sizes can be obtained with higher calcinationtemperatures. The features of the Er₂O₃:SiO₂ nanoparticles-glasscomposite system according to the present invention are listed, asfollows:

(1) Strong magnetic field dependence in the dielectric constant ofnanocrystalline phase pure Er₂O₃ at different temperature is observed.

(2) Such colossal MD behavior in this nanoparticles-glass compositesystem at near room temperature is observed in the context of themagnetic spin and the dipole coupling through the lattice, so that it isadvantageous to develop magnetoresistance change effects associated withnanoparticle size and concentration.

(3) Conduction mechanism in this nanoparticles-glass composite system isclosely related to the thermally activated oxygen vacancies, which canbe controlled by annealing the nanoparticles-glass composite system inoxygen atmosphere.

Based on the foregoing features, referring now to FIG. 9, the Er₂O₃:SiO₂nanoparticles-glass composite system according to the present inventioncan be used as a composite dielectric material and suitably applied to adielectric layer 10, wherein the dielectric layer 10 may be sandwichedbetween two electrode layers 11, 12. The matrix 101 of the dielectriclayer 10 can be silicon dioxide (SiO₂). Furthermore, the matrix 101 isdoped with the glass composite of nanoparticles 102 and silicon dioxide,wherein the nanoparticles 102 is preferably nanoparticles at leastincluding rare earth metal oxide, such as erbium oxide Er₂O₃, europiumoxide Eu₂O₃ or the mixture thereof, but the nanoparticles 102 mayinclude other composition, such as other silicon dioxide different fromthe silicon dioxide of the matrix 101. The present invention can controlthe predetermined calcination temperature (ranged from 700° C. to 1000°C.) to suitably adjust the size (ranged from 2 nm to 10 nm) of thenanoparticles 102 for the purpose of providing a high dielectric valuefor the dielectric layer 10. Moreover, an electronic element 13longitudinally passes through the dielectric layer 10 to electricallyconnect between the two electrode layers 11, 12, wherein the electronicelement 13 is preferably a gate electrode of a transistor unit.

In one embodiment, the dielectric layer 10, the electrode layers 11, 12and the electronic element 13 are all formed on an active surface of awafer 14, wherein the wafer 14 is preferably a silicon wafer, and thestacked number of the dielectric layer 10, the electrode layers 11, 12and the electronic element 13 can be one stack, two stacks or more, soas to construct surface circuit pattern structures on the wafer 14.After forming the dielectric layer 10, the electrode layers 11, 12, theelectronic element 13 and other structural layers of integrated circuits(not-shown), a back surface of the wafer 14 is suitably ground to reducethe thickness thereof, and then suitably cut into a plurality of chips(not-shown).

In the present invention, the manufacturing method of the dielectriclayer 10 uses a wet sol-gel process. For example, the wet sol-gelprocess may comprise the following steps of: mixingtetraethylorthosilicate (TEOS) and a precursor dopant (i.e. erbiumchloride (Er₂Cl₃) with a dopant concentration of 0.5 mol %) into asilica gel; and processing the silica gel by calcination to reach apredetermined maximum calcination temperature ranged from 700° C. to1000° C., so that the silica gel is converted into a glass composite ofthe rare earth metal oxide (i.e. erbium oxide (Er₂O₃)) and the silicondioxide (SiO₂) to thus form a composite dielectric material havingnanoparticles 102 of the rare earth metal oxide, wherein the compositedielectric material is applied to a surface of a semiconductor wafer 14to form a thin layer (i.e. the dielectric layer 10) on the surface ofthe wafer 14, wherein the dielectric layer 10 comprises the glasscomposite of the rare earth metal oxide and the silicon dioxide of thecomposite dielectric material. The matrix 101 of the dielectric layer 10is silicon dioxide which can be the silicon dioxide in the glasscomposite or other silicon dioxide come from another sol-gel process orother means. For example, in an alternative embodiment, the glasscomposite of the rare earth metal oxide and the silicon dioxide isfurther mixed with TEOS in another sol-gel process to obtain a mixturesolution, and the mixture solution is applied onto the surface of thesemiconductor wafer 14 by spin coating to form a silica gel layer whichis then calcined by a similar calcination and melt if necessary, so asto form a dielectric layer 10 having the glass composite of the rareearth metal oxide and the silicon dioxide and the silica matrix.

On the other hand, according to other embodiments of the presentinvention, the erbium chloride (Er₂Cl₃) also can be replaced by europiumchloride (Eu₂Cl₃) or other rare earth metal chloride, wherein the erbiumoxide (Er₂O₃) is correspondingly replaced by europium oxide (Eu₂O₃) orother rare earth metal oxide. Except for erbium (Er) and europium (Eu),the rare earth metal used by the present invention also can be selectedfrom lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd),promethium (Pm), samarium (Sm), gadolinium (Gd), terbium (Tb),dysprosium (Dy), holmium (Ho), thulium (Tm), ytterbium (Yb), lutetium(Lu), scandium (Sc), yttrium (Y) or the combination thereof.

As described above, in comparison with the traditional high-k materialwhich has magnetodielectric (MD) response but the reliability andstability thereof is still insufficient, the present invention as shownin FIG. 1 uses the sol-gel route to dope nanoparticles of rare earthoxides (such as erbium oxide Er₂O₃ or europium oxide Eu₂O₃) into SiO₂glass matrix, so as to form a glass composite system used as compositedielectric material which is also applied to a dielectric layer of asemiconductor wafer. The composite dielectric material can show colossaldielectric response and magnetodielectric effect under an externallyapplied magnetic field, so that it can increase the dielectriccoefficient of the dielectric layer of the semiconductor wafer and lowerthe leakage current and power consumption thereof. As a result, it isadvantageous to develop a multifunctional integrated circuit which cannormally operate at higher temperature.

The present invention has been described with a preferred embodimentthereof and it is understood that many changes and modifications to thedescribed embodiment can be carried out without departing from the scopeand the spirit of the invention that is intended to be limited only bythe appended claims.

1. A manufacturing method of a composite dielectric material doped withrare earth metal oxide, comprising steps of: mixingtetraethylorthosilicate (TEOS) and at least one type of rare earth metalchloride into a silica gel; and processing the silica gel by calcinationto reach a predetermined calcination temperature ranged from 700° C. to1000° C., so that the silica gel is converted into a glass composite ofrare earth metal oxide and silicon dioxide to thus form a compositedielectric material having nanoparticles of the rare earth metal oxide,wherein the particle diameter of the nanoparticles is ranged from 2 nmto 10 nm, wherein the composite dielectric material is applied to asurface of a semiconductor wafer to form a dielectric layer, and thedielectric layer comprises the glass composite of the rare earth metaloxide and the silicon dioxide of the composite dielectric material. 2.The manufacturing method of the composite dielectric material doped withrare earth metal oxide according to claim 1, wherein the rare earthmetal is selected from erbium, europium or the mixture thereof.
 3. Themanufacturing method of the composite dielectric material doped withrare earth metal oxide according to claim 1, wherein the surface of thewafer has at least two electrode layers, and the dielectric layer isdisposed between the electrode layers.
 4. The manufacturing method ofthe composite dielectric material doped with rare earth metal oxideaccording to claim 3, wherein the surface of the wafer has a pluralityof electronic elements which pass through the dielectric layer to beelectrically connected the at least two electrode layers with eachother.
 5. The manufacturing method of the composite dielectric materialdoped with rare earth metal oxide according to claim 1, wherein theconcentration of the rare earth metal chloride doped in the TEOS isranged from 0.1 mole % to 1.0 mol %.
 6. The manufacturing method of thecomposite dielectric material doped with rare earth metal oxideaccording to claim 1, wherein the concentration of the nanoparticles ofthe rare earth metal oxide doped in the silicon dioxide is ranged from0.1 mole % to 1.0 mol %.
 7. The manufacturing method of the compositedielectric material doped with rare earth metal oxide according to claim1, wherein before processing the silica gel by calcination, keepingstationary to dry the silica gel of the TEOS and the rare earth metalchloride.
 8. The manufacturing method of the composite dielectricmaterial doped with rare earth metal oxide according to claim 1, whereinwhen processing the silica gel by calcination, the silica gel of theTEOS and the rare earth metal chloride is processed by multi-stepcalcinations to form the composite dielectric material doped with thenanoparticles of the rare earth metal oxide embedded in the silicondioxide.
 9. The manufacturing method of the composite dielectricmaterial doped with rare earth metal oxide according to claim 1, whereinafter forming the composite dielectric material, further comprising:mixing the glass composite of the rare earth metal oxide and the silicondioxide with TEOS in another sol-gel process to obtain a mixturesolution; applying the mixture solution onto a surface of asemiconductor wafer by spin coating to form a silica gel layer; andprocessing the silica gel layer by calcination, so as to form adielectric layer having the glass composite of the rare earth metaloxide and the silicon dioxide and a silica matrix, wherein the silicondioxide of the silica matrix is different from the silicon dioxide ofthe nanoparticles of the glass composite.